Left ventricular outflow tract obstruction following aortic valve replacement: A review of risk factors, mechanism, and management

The presence of dynamic left ventricular outflow tract obstruction (LVOTO) can complicate the postoperative course of patients undergoing surgical aortic valve replacement (AVR). The phenomenon of LVOTO is a consequence of an interplay of various pathoanatomic mechanisms. The prevailing cardiovascular milieu dictates the hemodynamic significance of the resultant LVOTO in addition to the anatomical risk factors. A thorough understanding of the predisposing factors, mechanism, and hemodynamic sequel of the obstruction is pivotal in managing these cases. A comprehensive echocardiographic examination aids in risk prediction, diagnosis, severity characterization, and follow-up of management efficacy in the setting of postoperative LVOTO. The armamentarium of management modalities includes conservative (medical) and surgical options. A stepwise approach should be formulated based on the physiological and anatomical substrates predisposing to LVOTO. The index phenomenon occurs more frequently than appreciated and should be considered when the post-AVR patients exhibit hemodynamic instability unresponsive to conventional supportive measures. The present article provides an overview of various peculiarities of this under-recognized phenomenon in the context of the perioperative management of patients undergoing AVR.

Bidirectional Glenn with interruption of antegrade pulmonary blood flow: Which is the preferred option: Ligation or division of the pulmonary artery.

We report a rare complication of massive aneurysm of the proximal ligated end of the main pulmonary artery which occurred in the setting of a patient with a functionally univentricular heart and increased pulmonary blood flow undergoing superior cavopulmonary connection. Awareness of this possibility may guide others to electively transect the pulmonary artery in such a clinical setting

Short‑term prognostic value of perioperative coronary sinus‑derived‑serum cardiac troponin‑I, creatine kinase‑MB, lactate, pyruvate, and lactate‑pyruvate ratio in adult patients undergoing open heart surgery.

Objectives: To investigate the release pattern of different cardiac metabolites and biomarkers directly from the coronary sinus (CS) and to establish the diagnostic discrimination limits of each marker protein and metabolites to evaluate perioperative myocardial injury in patients undergoing cardiac surgery under cardiopulmonary bypass (CPB). Patients and Methods: Sixty-eight patients undergoing first mitral and/or aortic valve replacements with/without coronary artery bypass grafting and Bentall procedure under CPB and blood cardioplegic arrest were studied. All cardiac metabolites and biomarkers were measured in serial CS-derived blood samples at pre-CPB, immediate post aortic declamping, 10 minutes post-CPB and 12 hrs post-CPB. Results: Receiver operating characteristic curve analysis of cardiac biomarkers indicated lactate-pyruvate ratio as the superior diagnostic discriminator of myocardial injury with an optimal “cut-off” value >10.8 immediately after aortic declamping (AUC, 0.92; 95% CI: 0.85-0.98). Lactate was the second best diagnostic discriminator of myocardial injury with an optimal “cut-off” value >2mmol/l at immediately after aortic declamping (AUC, 0.89; 95% CI: 0.80-0.96). Cardiac troponin-I was the third best diagnostic discriminator of myocardial injury with an optimal “cut-off” value >2.1ng/ml at immediately after aortic declamping (AUC, 0.88; 95% CI: 0.80- 0.95). Creatine kinase-MB was the fourth best diagnostic discriminator of myocardial injury with an optimal “cut-off” value >58 log units/ml prior to decanulation (AUC, 0.85; 95% CI: 0.78-0.94). Conclusions: Measurable cardiac damage exists in all patients undergoing cardiac surgery under cardioplegic arrest. The degree of myocardial injury is more in patients with poor ventricular function and those requiring longer aortic clamp time. CS-derived lactate-pyruvate ratio, lactate, cTn-I served as superior diagnostic discriminators of peri-operative myocardial damage.

Idiopathic left ventricular outflow tract pseudoaneurysm.

Left ventricular outflow tract (LVOT) pseudoaneurysm is a rare occurrence and may produce clinically unpredictable symptoms. A very few cases of LVOT pseudoaneurysm are reported and there has always been a predisposing factor in these reported cases such as history of infective endocarditis, myocardial infarction, prosthetic aortic valve replacement or chest trauma. Our patient did not have the above predisposing conditions. Intra operative transesophageal echocardiography helped patient management and guided the surgical team in securing and isolation of the aneurysmal sac from the LVOT.

Is EuroSCORE applicable to Indian patients undergoing cardiac surgery.

Indian patients undergoing cardiac surgery have different demographics, clinical profile as well as risk profile, compared to the western population. The purpose of this study was to validate the European System for Cardiac Operative Risk Evaluation (EuroSCORE) risk stratification model in Indian patients undergoing cardiac surgery in a single cardiac center. Data from 1000 consecutive adult patients undergoing cardiac surgery (coronary artery bypass grafting or valve surgery) were prospectively collected as per the EuroSCORE model. The model's validity was assessed on the basis of its calibration power (Hosmer-Lemeshow test) and discriminatory power [area under receiver operating characteristic curve]. The patients were divided into three risk groups on the basis of their EuroSCORE. The Hosmer-Lemeshow test revealed a good calibration power (P = 0.73) and the area under the ROC curve was 0.8278, suggesting a good discriminative power. The predicted mortality was similar to observed mortality in low- and moderate-risk patients but the observed mortality in high-risk patients (15.6%) was double that of predicted mortality (7.5%). The risk factors prevalent in European population were not observed in Indian population. EuroSCORE accurately predicts mortality in low and moderate-risk Indian patients undergoing cardiac surgery but is less predictive for high-risk Indian patients. Updating and improvisation of EuroSCORE by incorporation of risk factors associated with rheumatic valvular heart disease which is more prevalent in India, may enable it to accurately predict mortality in high-risk patients also.

Comparison of three dose regimens of aprotinin in infants undergoing the arterial switch operation.

To determine the most effective dose regimen of aprotinin for infants undergoing arterial switch operation for transposition of the great arteries in reducing blood loss and postoperative packed red blood cell (PRBC) requirements. A total of 24 infants scheduled for arterial switch operation for transposition of the great arteries were included in the study. The infants were randomly assigned to one of the three groups. Group I (n = 8) patients received aprotinin in a dose of 20,000 kallikrein inhibiting units (KIU)/kg after induction of anesthesia, 20,000 KIU/kg was added to the pump prime, and 20,000 KIU/kg/hour infusion for three hours after weaning from bypass; group II (n = 8) patients received aprotinin 30,000 KIU/kg after induction of anesthesia, 30,000 KIU/kg was added to the pump prime and 30,000 KIU/Kg/hour infusion for three hours after weaning from bypass; group III patients (n = 8) received aprotinin 40,000 KIU/kg after induction of anesthesia, 40,000 KIU/kg was added to the pump prime and 40,000 KIU/kg/hour infusion for three hours after weaning from bypass. Postoperatively, the cumulative hourly blood loss and PRBC requirements were noted up to 24 hours from the time of admission in the intensive care unit (ICU). Use of blood and blood products were noted. Coagulation parameters such as hematocrit, activated clotting time (ACT), fibrinogen, prothrombin time (PT), international normalized ratio (INR), platelet count, and fibrin degradation products (FDP) were investigated before cardiopulmonary bypass (CPB), after protamine administration, and at four hours postoperatively in the ICU. The number of infants reexplored for increased mediastinal drainage was recorded. Renal functions were monitored by measuring urine output (hourly) and serum urea (mg%) and serum creatinine (mg%) at 24 hours. The sternal closure time was comparable in all the three groups. Cumulative blood loss (ml/kg/24 hours) was greatest in group I (17.30 ± 7.7), least in group III (8.14 ± 3.17), whereas in group II, it was 16.45 ± 6.33 (P = 0.019 group I versus group III; (P = 0.036 group II versus group III). Postoperative PRBC requirements were significantly less in high dose group III (P = 0.008, group I versus III; p = 0.116, group II versus group III) . Tests for coagulation performed at four hours postoperatively, viz. ACT, PT, INR, FDP, and platelets were comparable in the three groups. Urine output on CPB was comparable in all the groups. Serum urea and creatinine showed no significant difference between the three groups twenty four hours postoperatively. Aprotinin dosage regimen of 40,000 KIU/kg at induction, in CPB prime and postoperatively for three hours was most effective in reducing postoperative blood loss and PRBC transfusion requirements. Aprotinin does not have any adverse effect on renal function.

Effect of single intraoperative dose of amiodarone in patients with rheumatic valvular heart disease and atrial fibrillation undergoing valve replacement surgery.

Maintenance of sinus rhythm (SR) is superior to rate control in atrial fibrillation (AF). In order to achieve SR, we administered single-dose intravenous amiodarone intraoperatively and evaluated its effect on conversion of rheumatic AF to SR in patients undergoing valvular heart surgery. Patients were randomly assigned to amiodarone (n = 42) or control (n = 40) group in a double blind manner. The amiodarone group received amiodarone (3 mg/kg) intravenously prior to the institution of cardiopulmonary bypass and the control group received the same volume of normal saline. In the amiodarone group, the initial rhythm after the release of aortic cross clamp was noted to be AF in 14.3% (n = 6) and remained so in 9.5% (n = 4) of patients till the end of surgery. In the control group, the rhythm soon after the release of aortic cross clamp was AF in 37.5% (n = 15) (p = 0.035) and remained so in 32.5% (n = 13) of patients till the end of surgery (p = 0.01). At the end of first post-operative day 21.4% (n = 9) of patients in amiodarone group and 55% (n = 22) of patients in control group were in AF (p = 0.002). The requirement of cardioversion/defibrillation was 1.5 (+/-0.54) in amiodarone group and 2.26 (+/-0.73) in the control group (p = 0.014), and the energy needed was 22.5 (+/-8.86) joules in the amiodarone group and 40.53 (+/-16.5) in the control group (p = 0.008). A single intraoperative dose of intravenous amiodarone increased the conversion rate of AF to normal sinus rhythm, reduced the need and energy required for cardioversion/defibrillation and reduced the recurrence of AF within one day.

Evaluation of efficacy of intranasal midazolam, ketamine and their mixture as premedication and its relation with bispectral index in children with tetralogy of fallot undergoing intracardiac repair.

We compared the efficacy of intranasal midazolam, ketamine and their mixture as premedication in children with tetralogy of Fallot (TOF) using bispectral index (BIS), sedation score and separation score at the time of separation from parent. Sedation score at the time of intravenous cannulation was also measured. Children with TOF physiology were randomly divided into three equal groups of 20 each. Group-A received intranasal ketamine (10 mg/Kg), Group-B received intranasal midazolam (0.2 mg/Kg), while Group-C received a mixture of ketamine (7.5 mg/Kg) and midazolam (0.1 mg/Kg) intranasally. After 30 minutes of premedication, sedation and separation score were noted. BIS values were recorded at 5 minutes intervals. A 4-point scale for sedation, separation and acceptance of intravenous cannulation was used. Sedation was good in midazolam group (group B-3.25 +/- 0.44), but the separation and acceptance of intravenous catheter was poor (2.9 +/- 0.31 and 2.85 +/- 0.37 respectively). Sedation scores in group A and C were excellent (3.75 +/- 0.44 and 3.80 +/- 0.41 respectively). Separation from parent was excellent in group A (ketamine) and group C (mixture) (group A- 3.90 +/- 0.28 and group C- 3.83 +/- 0.35 respectively). Children of both these groups allowed easy placement of intravenous cannula. At BIS values < 90, the sedation achieved was good. BIS values decreased with increase in sedation scores in groups who received intranasal midazolam and mixture containing ketamine and midazolam (group B and C respectively), while it remained high in children who received ketamine. We conclude that intranasal ketamine is better than intranasal midazolam. The combination of two is better than midazolam alone but provides no benefit as compared with ketamine alone.

A Comparison of aminocaproic Acid and Tranexamic Acid in Adult Cardiac Surgery.

We compared Aminocaproic acid with tranexamic acid, prospectively in 120 patients undergoing coronary artery bypass surgery on cardiopulmonary bypass. Patients were assigned to one of the 3 groups. Group A (n=40) did not receive any drug and acted as the control group. Group B (n=4) received aminocaproic acid 100 mg/kg each at anaesthetic induction, on bypass and after protamine reversal of heparin. group C (n=40) received tranexamic acid 10 mg/kg each at anaesthetic induction, on bypass and after protamine reversal of heparin. Postoperative blood loss at 24 hours, blood and blood product usage, and re-exploration rates were recorded, and tests for coagulation were performed at 6 hours postoperatively. It was found that blood loss in group A at 24 hours (780+/-120 mL) was significantly greater than Group B (360+/-90 mL) and Group C (215+/-70 mL). Plasma and platelet concentrate use in Group A (215+/-30 mL and 150+/-30 mL) was greater than Group B (190+/-20 mL and 75+/-30 mL) and Group C (185+/-20 mL and 80+/-30 mL). Re- explorations in Group A, 8/40 (20%) were greater than Group B, 2/40 (5%) and Group C, 2/40 (5%). Coagulation tests revealed better preservation of fibrinogen and lower levels of fibrin degradation products, in group B and C. These two groups were however statistically indistinguishable in respect to all the parameters studied, when compared with each other. It was concluded that both the antifibrinolytic agents in the doses studied were equally effective in reducing postoperative blood loss, blood and blood products usage and re-exploration rates. Coagulation parameters were better preserved as compared to the control group.

Tranexamic acid in paediatric cardiac surgery.

BACKGROUND & OBJECTIVES: Antifibrinolytic agents are used commonly in adult cardiac surgery to reduce postoperative blood loss. Paucity of literature on the use of a newer antifibrinolytic agent tranexamic acid (TA) in children undergoing cardiac surgery promoted us to conduct this study in children with cyanotic heart disease. METHODS: One hundred and twenty consecutive children with cyanotic heart disease were randomised into two groups. Control (group A) (n=24) given no drug while the study (group B, n=96) group was given tranexamic acid 10 mg/kg each after anaesthetic induction, on bypass and after protamine at the end of bypass. Postoperatively, total mediastinal chest tube drainage and blood and blood product usage at 24 h were recorded. Tests of coagulation including activated clotting time, fibrinogen, fibrin degradation products and platelet count were performed at 6 h postoperatively. RESULTS: The two groups were comparable in terms of demographic characteristics such as age, sex, weight, operations performed, and preoperative haematocrit. Postoperatively, group B, had a significantly (P<0.05) lower blood loss, blood and blood product usage, re-exploration rate compared to the control group. There was preservation of fibrinogen and lower levels of fibrin degradation products in group B. INTERPRETATION & CONCLUSION: Tranexamine acid was highly effective in reducing post-operative blood loss, blood and blood product usage in children with congenital cyanotic heart disease undergoing corrective surgery.